Crosslinked foam which has inner-cavity structure, and process of forming thereof

ABSTRACT

A method and device for forming a cross-linked foam and a cross-linked foam are provided. The method includes the steps of preparing at least one foaming material for cross-linked foaming, the foaming material processed to have a plane or three-dimensional shape; forming at least one interfacing pattern on a surface of at least one of the foaming material using at least one interfacing material that prevents chemical and physical interaction between the foaming materials; and forming a cross-linked foam by foaming the foaming material having the interfacing pattern thereon, the cross-linked foam having a foam body and an internally-formed surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cross-linked foam and a manufacturingmethod thereof. More specifically, it relates to a cross-linked foamhaving various inner cavity structures formed by an internally-formedsurface and a method and device for forming the inner cavity structuresimultaneously with a body of the cross-linked foam.

2. Discussion of the Related Art

FIG. 30 is a flow chart illustrating process steps for manufacturingcross-linked foams according to a related art. In step S10, sourcematerials including main material such as diverse resins and otheradditives are first weighed in accordance with a designed mixturestandard depending on what kind of cross-linked foam is fabricated. Thenthe weighed resins and additives are mixed with a cross-liking agent anda foaming agent in a hermetical mixer or kneader in a milling process.Therefore, a mixed chemical compound is prepared.

In step S20, the prepared chemical compound is provided into a calendarroll or an extruding machine. The calender roll transforms the chemicalcompound in a form of sheet or film, e.g., a two dimensional shape, andthe extruding machine transforms the chemical compound in a form ofpellet, e.g., a three dimensional shape.

Step S30 shows various process steps for forming a desired cross-linkedfoam. The process of forming the cross-linked foam may be classifiedinto a pressure cross-linked foaming method (pressure cross-linked foammolding) and a normal pressure cross-linked foaming method depending onmachinery and equipment for the processes considering shapes andproperties of the desired cross-linked foam.

The pressure cross-linked foaming method mainly uses a metallic mold(s)to make the desired cross-linked foam, and applies heat and pressure tothe chemical compounds after an input of the chemical compound into theinner parts of the metallic mold(s). Therefore, the cross-linked foamhaving a discontinuous pattern is formed in accordance with an innerpart shape of the metallic mold(s) by a decomposition action of thefoaming agent. Such pressure cross-linked foaming method may includes,for example, a compression-press cross-linked foam molding method thatuses a press machine, and a injection-press cross-linked foam moldingmethod that uses an injection machine, as shown in the step S30 of FIG.30.

When using the compression-press cross-linked foam molding method, thesource materials are first put into the opened mold, and then the moldincluding the source material is closed. When using the injection-presscross-linked foam molding method, the source materials are put into theairtight injection mold. However, both in the compression-press andinjection-press cross-linked foam molding methods, once the sourcematerial is provided into the mold, equipment such as press machineapplies heat and pressure to the closed mold to foam the source materialinto a cross-linked foam

In step S40, the applied pressure is released, and then the closed moldis open to de-mold the cross-linked foam. The de-molded material is thencured for a time period and cooled down to a desired temperature. Instep S50, the cured and cooled cross-linked foam is then cut and trimmedto be a final product.

Although not shown in FIG. 30, the pressure cross-linked foaming methodmay also include a compression-rotary press cross-linked foam moldingmethod where heating rolls and metallic press/conveyer belts are used toapply heat and pressure to the source materials for the cross-linkedfoam by way of inserting the source materials between the heating rollsand the metallic press/conveyer belts. Alternatively, thecompression-rotary press cross-linked foam molding method may insert thesource materials continuously with other textile materials or rubberymaterials between the heating rolls and the metallic press/conveyerbelts, whereas the foaming of the source material is induced at a pointwhere the pressure is discharged. Thus, the cross-linked foam may havecontinuous and uniform surface and cross section.

The pressure cross-linked foaming method applies heat and pressuredirectly to the source materials using the metallic moulds and rolls.The compression-press cross-linked foam molding method produces variouslarge or small industrial foams, for example, EVA, PE, rubbery large orsmall sponge panels, shoe components, sports goods and accessories, andthe like. The injection-press cross-linked foam molding method generallyproduces various industrial foams having individual shape, for example,EVA-based shoe components, sports protectors and goods, bags,accessories and the like. The compression-rotary press cross-linked foammolding method produces various industrial continuous roll types orlarge panel type foams, for example, EVA, PE or other rubbery continuousrolls.

Meanwhile, the normal pressure cross-linked foaming method is widelyused for forming a cross-linked foam having a continuous and uniformcross section. Unlike the pressure cross-linked forming method, thenormal pressure cross-linked foaming method produces the cross-linkedfoams without a direct heat and pressure infliction on the sourcematerials. The normal pressure cross-linked foaming method is classifiedinto a chemically cross-linked foaming method and an electronirradiation cross-linked foaming method.

The chemically cross-linked foaming method adds and mixes a chemicalcross-linking agent, a foaming agent, and an EVA based resin into apolyethylene resin that is a main source material. Thereafter, themixture is extruded into a pellet type foaming material as shown in stepS10 and S20 of FIG. 30. Then, through the step S30 of FIG. 30, thefoaming materials are inserted into a hopper of the extruding machinethat includes screws, heat appliers and extruding dies, and then theheat pre-determined by the material composition is applied to thefoaming materials. After that, the melted foaming material passesthrough the extruding dies to provide a continuous and uniform crosssection, and then the foaming material is foamed thereby (in step S30).

The electron irradiation cross-linked foaming method applies electronrays to a foaming material that is formed by extruding a polyethylene orpolypropylene resin mixed with other additives and agents, therebycross-linking the materials and heating the foaming material up to thefoaming-agent's decomposing temperature to make the foams. This electronirradiation cross-linked foaming method differs from the chemicallycross-linked foaming method in a way that this uses the electron rays toachieve the cross-linking and then heats the cross-linked foamingmaterial to foam the cross-linked foaming material.

Meanwhile, in step S40, the cross-linked foam is cured for a time periodand then cooled down to a certain temperature. In step S50, thecross-linked foam is then cut, trimmed and designed to be a finalproduct.

Although not shown, the normal pressure cross-linked foaming methodincludes a calender cross-linked foaming method in which a mixture of apolyvinyl chloride based or polyolefin based resin with a chemicalfoaming agent, a cross-linking agent (plasticizer in case of polyvinylchloride), a stabilizer and a surfactant is used. The calendercross-linked foaming method transforms the mixture into a continuous anduniform foaming material using the extruding machine, the storage milland the calender roll, and then the foaming material is heated in theheating chamber of a conveyor to be foamed under a normal pressurecondition. Thereafter, the foaming material is cooled down and cured fora time period to form the foams, and then a roll-shaped foam is obtainedby way of winding the foams on the take-up roll.

In step S60 of FIG. 30, the foams finally obtained through the pressurecross-linked foaming method or normal pressure cross-linked foamingmethod may be attached to one of other molded materials formed with amaterial that is the same as or different from the foaming material,textiles, woods and metallic materials depending on an end use, propertyand purpose of the foams and then be re-formed.

Such a re-forming method may be classified into a heat/cold moldcompression re-molding, a cold mold compression re-molding, a cold moldvacuum re-molding, and a blow re-molding. The heat/cold mold compressionre-molding method forces the cross-linked foam to be inserted into themold, and then the cross-linked foam in the mold is cooled down afterbeing heated and pressed. The cold mold compression re-molding methodpre-heats the cross-linked foam and then inserts it into the mold, andthereafter, the cross-linked foam is pressed and cooled down to form thefinalized foam. The cold mold vacuum re-molding method applies heat tothe cross-linked foam at a pre-determined temperature and then sucks theheated foam into the mold using a vacuum pressure, and thereafter, thefoam is cooled down and de-molded to form the finalized foam.Furthermore, the blow re-molding method applies heat to the cross-linkedfoam to be softened and then inserts the high-pressure gas or the liquidinto the cross-linked foam, such that the cross-linked foam is re-moldedin the mold and becomes the finalized foam after being de-molded.

The cross-linked foams formed by the related art cross-linked foamfabrication methods have the following characteristics. Thecompression-press cross-linked foam molding method of the pressurecross-linked foaming method inserts the source material shaped like asheet type or a particle type into the mold, and then applies heat tothat source material, thereby manufacturing the foam having a uniformphysical property. Furthermore, since the injection-press cross-linkedfoam molding method heats the source material in the cylinder of thefeeder and then melts the material so as to be inserted into the mold,the source material can have the uniform property in all parts and theproduced cross-linked foams may also have the uniform physicalcharacteristics.

Meanwhile, since the normal pressure cross-linked foaming method insertsthe source materials having a particle type into the extruding machineand then heats them to be softened, the cross-linked foam material canhave the uniform cross section and the uniform physical property in allparts, and also the finalized foam may have the uniform property in allportions. Although the source material is formed of the severalsubstances in the related art cross-linked foam fabrication, thefinalized foam also has the determined property having the uniformdensity because the source material is transformed into a single unifiedmaterial before the foam process. Moreover, in the related art methodsdescribed above, the foaming process does not make the foam havingdifferent density or different properties in every each portion becausethe same source material is used in the foam process. The related artcross-linked foaming method is hard to manufacture an inner cavitystructure having various shapes and formations inside the foam at thesame time when the foam is made. Therefore, the related art cross-linkedfoaming method does not make the density differentiation inside thefinalized foam.

Therefore, when manufacturing the cross-linked foam having the complexphysical properties and functions, the related art separately makes thecross-linked foams and then cuts, grinds and attaches the foams inadditional fabrication steps to produce the foam having the diversedensities and desired inner structures. However, such additionalprocesses may cause the fabrication difficulty, the low throughput andthe degradation of design and quality, such that the desiredcross-linked foam having the various physical properties and innerstructures is hardly obtained. Moreover, the related art describedhereinbefore may increase the process steps and costs and may causeindustrial wastes because the foams each having different physicalproperties and functions are separately manufactured and compounded.

To overcome the above-mentioned disadvantages, the Korean PatentApplication No. 2003-45282 titled “Method for Manufacturing EVA BasedFoam” has disclosed a method including steps of 1) mixing an EVA resin,a cross-linking agent, a foaming agent, a colorant, a filler, anadditive, and a rubber or a resin which can be mixed with the EVA resin,2) performing a low melting point spinning on the resultant composition,3) making the spinning filament into a tow or staple fiber to be used asa first material, selecting a second material from a group consisting ofa water soluble PVA based staple fiber, a polyester based staple fiberand a natural fiber, and producing a non-woven fabric by mixing thefirst and second materials, 4) melting out a dissolved matter from thenon-woven fabric, and 5) cross-linked foaming the non-woven fabric. Thismethod has merits in that an air pore structure is formed in the foam.However, the method disclosed in the above-described Korean PatentApplication No. 2003-45282 is not concerned with a method for designingor controlling the shape and structure of the inner surface shape andstructure of the foam, whereby the cross-linked foam could not have thedifferent densities and functions in the parts.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to cross-linked foams anda manufacturing method and device thereof that substantially obviatesone or more of the problems due to limitations and disadvantages of therelated art.

An advantage of the present invention is to provide a method and devicefor forming a cross-linked foam that has at least one inner cavitystructure and a cross-linked foam made by the method and device.

Another advantage of the present invention is to provide a method offorming cross-linked foam in which at least one interfacing pattern isformed between multi-layered foaming material and the interfacingpattern forms an inner cavity structure during a foaming process, and across-linked foam made by the method.

Another advantage of the present invention is to provide a method offorming a cross-linked foam in which a plurality of inner cavitystructures separated from each other are formed in the same cross-linkedfoam, and a cross-linked foam made by the method.

Another advantage of the present invention is to provide a method offorming a cross-linked foam in which at least one independent moldedlayer separable from an internally-formed surface is formed, and across-linked foam made by the method.

Another advantage of the present invention to provide a method offorming a cross-linked foam in which a pressure and a volume of air inan inner cavity structure can be controlled diversely, and across-linked foam made by the method.

Another advantage of the present invention is to provide a method offorming a cross-linked foam in which an inner cavity is filled withmaterials that are the same as or different from the cross-linked foam,and a cross-linked foam made by the method.

Another advantage of the present invention is to provide a method offorming a cross-linked foam in which an inner cavity structure caneasily be utilized as an air passage or a shock absorber, and across-linked foam made by the method.

Another advantage of the present invention is to provide a method offorming a cross-linked foam that can decrease a weight and increasephysical properties and functions such as a shock absorbing power, ashape recovery force and resilience, etc., and a cross-linked foam madeby the method.

Another advantage of the present invention is to provide a cross-linkedfoam that has differentiated physical properties and functions at itseach portion.

Additional features and advantages of the invention will be set forth inthe description which follows and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, across-linked foaming method comprises preparing at least one foamingmaterial for a cross-linked foaming, the foaming material processed tohave a plane or three-dimensional shape; forming at least oneinterfacing pattern on a surface of at least one of the foaming materialusing at least one interfacing material that prevents chemical andphysical interaction between the foaming materials; and forming across-linked foam by foaming the foaming material having the interfacingpattern thereon, the cross-linked foam having a foam body and aninternally-formed surface.

In another aspect, the present invention provides a cross-linked foamthat comprises a foam body; and at least one inner cavity structureformed inside the foam body, wherein the foam body and the inner cavitystructure are formed simultaneously.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the presentinvention and together with the description serve to explain theprinciples of that invention. In the drawings:

FIG. 1 illustrates a manufacturing process of a cross-linked foam havingmore than one internally-formed surface according to a first embodimentof the present invention;

FIG. 2 illustrates a manufacturing process of a cross-linked foamaccording to a second embodiment of the present invention;

FIG. 3 illustrates a manufacturing process of a cross-linked foamaccording to a third embodiment of the present invention;

FIG. 4 illustrates a manufacturing process of a cross-linked foamaccording to a fourth embodiment of the present invention;

FIGS. 5 a and 5 b show manufacturing processes of a cross-linked foamaccording to a fifth embodiment of the present invention;

FIG. 6 illustrates a manufacturing process of a cross-linked foamaccording to a sixth embodiment of the present invention;

FIG. 7 illustrates a cross-linked foam having an air ventilatingstructure to improve a buffering function and an air permeabilityaccording to a seventh embodiment of the present invention;

FIG. 8 illustrates a manufacturing process of a cross-linked foamaccording to an eighth embodiment of the present invention;

FIG. 9 illustrates a manufacturing process of a cross-linked foamaccording to a ninth embodiment of the present invention;

FIG. 10 illustrates a manufacturing process of a cross-linked foamaccording to a tenth embodiment of the present invention;

FIG. 11 illustrates a manufacturing process of a cross-linked foamaccording to an eleventh embodiment of the present invention;

FIG. 12 illustrates a manufacturing process of a cross-linked foamaccording to a twelfth embodiment;

FIG. 13 illustrates a manufacturing process of a cross-linked foamaccording to a thirteenth embodiment of the present invention;

FIG. 14 illustrates a manufacturing process of a cross-linked foamaccording to a fourteenth embodiment of the present invention;

FIG. 15 illustrates a manufacturing process of a cross-linked foamaccording to a fifteenth embodiment of the present invention;

FIG. 16 illustrates a manufacturing process of a cross-linked foamaccording to a sixteenth embodiment of the present invention;

FIGS. 17 a to 17 v illustrate diverse examples of the cross-linked foamaccording to the present invention.

FIGS. 18 a to 18 f illustrate exemplary applications of the cross-linkedfoam of the present invention to many parts of a shoe;

FIGS. 19 a to 19 e illustrate exemplary applications of the cross-linkedfoam of the present invention to the uppers of a shoe;

FIG. 20 illustrates an exemplary application of the cross-linked foam ofthe present invention to an inner sole of a shoe;

FIGS. 21, 22 a and 22 b illustrate exemplary applications of thecross-linked foam of the present invention to a midsole of a shoe;

FIG. 23 illustrates exemplary applications of the cross-linked foam ofthe present invention to an outsole of a shoe;

FIG. 24 illustrates exemplary applications of the cross-linked foam ofthe present invention to a sockliner of a shoe;

FIG. 25 illustrates exemplary applications of the cross-linked foam ofthe present invention to a foam padding of a shoe;

FIG. 26 illustrate exemplary applications of the cross-linked foam ofthe present invention to an instep pad of a shoe;

FIG. 27 illustrates exemplary applications of the cross-linked foam ofthe present invention to a stiffener of a shoe;

FIGS. 28 a and 28 b illustrate exemplary applications of thecross-linked foam of the present invention to molded components of theuppers of a shoe;

FIGS. 29 a to 29 t illustrates a wide variety of applications where thecross-linked foam of the present invention can be employed;

FIG. 30 is a flow chart illustrating process steps for manufacturingcross-linked foams according to a related art; and

FIG. 31 is a flow chart illustrating process steps for manufacturingcross-linked foams according to the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to illustrated embodiments of thepresent invention, examples of which are shown in the accompanyingdrawings. Wherever possible, similar reference numbers will be usedthroughout the drawings to refer to the same or similar parts.

FIG. 31 is a flow chart illustrating process steps for manufacturingcross-linked foams according to the present invention. As shown in FIG.31, the forming method of the present invention includes a step ofmixing source materials (S100), a step of shaping the mixed sourcematerials (S200), a step of selecting an interfacing material(s) (S300),a step of forming an interfacing pattern(s) using the selectedinterfacing material (S400), a step of foaming a foaming material havingthe interfacing pattern to form a foam (S500), a step of cooling andcuring the foam (S600), and a step of finalizing the foam (S700).

The step S100 selects a main resin as a source material among thevarious materials depending on the desired cross-linked foam'savailabilities and physical properties, and then mixes the main resinwith the other additives and agent. After planning the materialcomposition, the source material and the sub materials are weighed bydesired amounts in accordance with the material composition plan, andthen the source material and sub materials are mixed in the airtightmixer or kneader. The step S100 may include adding a cross linking agentand a foaming agent into the mixture using an open mill.

The source material used in the step S100 can be selected from syntheticmaterials each having a possibility of becoming a foam using one ofvarious cross-linked foaming methods. For example, such syntheticmaterials may include synthetic resins such as an EVA based resin, apolyolefin based resin containing PEs of a variety of densities, apolyvinyl based resin, a polyurethane basted resin, and LDPE (lowdensity polyethylene)-added EVA, a copolymer thereof, a blend thereof,or a mixture thereof; a natural or synthetic rubber constituted by amixture of a natural rubber, a styrene butadiene rubber (SBR) based, apoly-butadiene rubber (BR) based, an poly-isoprene rubber (IR) based, achloroprene rubber (CR) based, an nitrile rubber (NRB) based, an EPDMrubber based, an ethylene-propylene rubber (EPR) based, and an acrylrubber (AR) based rubber, and/or an styrene butadiene rubber (SBR) addedneoprene rubber (NR); and a composite material including an EPDM rubberadded ethylene-vinyl acetate (EVA) and a poly-vinyl chloride (PVC) addednitrile butadiene rubber (NBR).

However, it is recommended to adopt EVA (ethylene-vinyl acetate) thatcan contain a variable percentage of an amount of vinyl acetate (VA %)or the polyethylene (PE) based synthetic resin having various densitiesas the source material.

When more than one source material among the above-mentioned materialsis properly mixed with the sub materials to be a composite through theabove-mentioned composition process, the composite becomes a foamingmaterial with the foaming action suppressed by the calender roll or theextruder. At this time, the foaming material has a planar shape such asa film or sheet, or a three-dimensional shape such as a pellet, at stepS200.

The foaming material according to the present invention is not limitedto a specific shape or type, but the foaming material is weighedwhenever it is used as a particle or sheet type at every foamingprocess. Further, when the foaming material is applied to the specificembodiment described hereinafter, the foaming material is recommended tohave a plane shape, particularly a film shape, which has a precisesurface roughness, regarding the advisable use. Namely, the EVA based orPE based film, or the material having the same surface roughness as themcan be used for the foaming material.

Meanwhile, when converting a primary foaming material, such as thecomposite completed by the injection machine or the pellet having thefoaming-inhibited state, into a secondary foaming material having thefoaming-inhibited characteristic by the injection method, the primaryfoaming material having the particle type is softened inside a cylinderat a low temperature, e.g., 70-90 degrees Celsius, and then the softenedprimary foaming material is filled into an empty space of the moldingdie to perform the low temperature formation, e.g., less than 50 degreesCelsius. Therefore, at this time of forming the second foaming material,the foaming agent inside the primary foaming material is notdecompositioned while the secondary foaming material is made.

When the press-type method is utilized, the second foaming material canbe obtained if the primary foaming material having the sheet, film orpellet shape formed by the mold is processed at a condition where thefoaming agent is not decompositioned (for example, at a heatingtemperature of less than 60-80 degrees Celsius, under the pressure ofmore than 150 Kg/cm², and at a cooling temperature of less than 50degrees Celsius).

The normal pressure cross-linked foaming method, which forms thecontinuous pattern shape unlike the pressure cross-linked foamingmethod, softens the primary foaming material using the extrusion methodsimilar to the injection method, and then produces the material havingthe continuous and uniform cross section. Therefore, any type of shapesof foaming material can be applied to the present invention only if itis possible to form the interfacing pattern on the foaming material withthe foaming action suppressed.

Once the foaming material is prepared (S300), at least one interfacingpattern is formed on the surface of the foaming material in a specificshape (S400).

The interfacing pattern is for forming an internally-formed surface thatforms an inner cavity structure in the cross-linked foam during thecross-linked foaming process, and the interfacing pattern is also forpreventing the physical or chemical interaction between the foamingmaterials that face each other across the interfacing pattern.

The material for the interfacing pattern may be liquids havingviscosity, powder or solid having a certain shape such as films, whichis able to prevent the interaction between the foaming materials duringthe cross-linked foaming process. For example, the interfacing materialmay be selected from a group consisting of natural or synthetic paintsor inks, natural or synthetic resins, papers, textiles, non-wovenfabrics, and rubbery materials. Additionally, when selecting theinterfacing material, it is considerable to be easily attached to thefoaming material, to have the repeated reappearance during the foamingprocess, to have the possibility of obstructing the cubical expansion ofthe foam during the foaming process, or to have the easy eliminationfrom the cross-linked foam if required after the foaming process.

The formation of the interfacing pattern may be achieved by printing,transcription, coating, deposition, lamination, spray, cloth attachment,inserting, attaching, or a modification thereof. In fact, any othermethod can be used as long as it is able to form the interfacingmaterial on the surface of the foaming material. However, when the inkor the like containing various kinds of resins dissolved is used as aninterfacing material, the printing method is desirably adopted informing the interfacing pattern. Further, if more than two interfacingpatterns are formed, each of the interfacing patterns may be formed withthe same or different material. A foaming agent, which is the same as ordifferent from the foaming agent contained in the foaming material, maybe added to the interfacing material.

Moreover, a step of combining a foaming material having no interfacingpattern with the foaming material having the interfacing pattern may befurther added. The foaming material having no interfacing pattern may bethe same material as or different material from the foaming materialhaving the interfacing pattern. A step of adding the material that isthe same as or different from the foaming material having theinterfacing pattern to the combined foaming material may be furtheradded. A step of winding the foaming material having the interfacingpattern on a roll may further be added to easily separate the foamingmaterial.

After completing the formation of the interfacing pattern on the foamingmaterial, the cross-linked foaming process is performed by the pressurecross-linked foaming method, the normal pressure cross-linked foamingmethod, or any modified method thereof. According to the press-typemethod and the injection-type method of the pressure cross-linkedfoaming method, the molding die is opened and then the foaming materialhaving the interfacing pattern is filled automatically orhand-operatedly into the hollow space of the molding die, therebyfoaming the foaming material by applying heat and pressure thereto. Inthe chemical or electron irradiation method of the normal pressurecross-linked foaming method, the foaming material having the interfacingpattern is provided before a heating process for foaming and then thefoaming process is performed (step S500 of FIG. 31). If the heat isapplied to the foaming material or if the electron rays are irradiatedon the foaming material during the cross-linked foaming process, thefoaming material is cross-linked in a gel state by the heat inflictionor the electron irradiation.

However, the foaming materials neighboring each other across theinterfacing pattern are not physically/chemically coupled andinterconnected until they reach the step of foaming. At this state, thefoaming materials cubically expand at a specific rate and then thecross-linked foams are made. Portions of the foaming materialscorresponding to the interfacing patterns are also cubically expanded atthe same ratio as the other portions during the foaming process.However, because the physical and chemical connection of the foamingmaterial is prevented by the interfacing pattern, an internally-formedsurface is formed in the cross-linked foam at a position correspondingto the interfacing pattern. The internally-formed surface forms an emptyspace, i.e., an inner cavity. A shape and structure of the inner cavitycan be easily controlled by changing a shape or material of the materialfor the interfacing pattern irrespective of manufacturing equipment andfacilities. A certain amount of gas (for example, nitrogen gas (N₂),carbon dioxide (CO₂)) that is generated by a decomposition action of thefoaming agent during the foaming process is trapped into the space (theinner cavity) formed by the internally-formed surface. The gas pressureof the inner cavity can be properly controlled by adding a certainamount of foaming agent or material that can increase a gas generationto the interfacing material before the foaming process. Whereas, the gaspressure in the inner cavity may be controlled by an externalair-pumping device.

If the pressure cross-linked foaming method is adopted to form thecross-linked foam of the present invention, a material same as ordifferent from the foaming material having the interfacing pattern maybe input into a residual space of the mold where the foaming materialhaving the interfacing pattern has already been laid, and then thosematerials may be foamed simultaneously to form the cross-linked foam. Acombination or modification of the pressure cross-linked foaming methodand the normal pressure cross-linked foaming method can be adopted foran embodiment of the present invention.

After the completion of foaming process, the foams are cooled down andcured to stabilize the property and size thereof at a predeterminedcondition at step S600 of FIG. 31. Thereafter, the foams are cut andtrimmed at step S700, thereby completing the cross-linked foamingprocess according to the present invention. However, it is possible tore-mold the cross-linked foams using a compression molding, a vacuummolding, or a blow molding that injects air or liquid, depending on ausage of the cross-linked foam as in step S800 of FIG. 31. Although theprimarily formed foams are re-molded, the shape and structure of theinternally-formed surface are not affected by the mold's shape andstructure or other equipment during the re-molding process. Meanwhile,the foaming process of the present invention may further include a stepof inserting or filling a material that is the same as or different fromthe foaming material into the empty space formed by theinternally-formed surface of the foam and then foaming the foamingmaterial having the inserted or filled material. Also, the presentinvention may further include a step of forming an air passage in thefoam extending from the surface of the foam to the internally-formedsurface and then injecting a material that is the same as or differentfrom the foaming material into the space formed by the internally-formedsurface through the air passage before the foaming process. The methodof injecting the material through the air passage makes it possible thata portion of the injected material is also formed on the surface of thefoam, such that the foam can have the unified/integrated appearancebetween the internally-formed surface and the outer foam surface,wherein the material in the space formed by the internally-formedsurface can be easily recognized from the outside. The type and phase ofthe material to be injected, filled or inserted into the space formed bythe internally-formed surface is not limited, and the injected, filledor inserted material can be adhered to the internally-formed surfaceusing an adhesive material depending on a kind of inserting material.

Now, a method for forming and controlling the shape of the inner cavitystructure of the cross-linked foam will be explained in detail inaccordance with the present invention.

Material Preparation for Manufacturing Cross-linked Foam

In the present invention, the selection of a source material formanufacture of a foam is provided in the following three types. Tables1-4 provide various examples of a material composition for forming across-linked foam according to the present invention.

Type A: This type mainly includes an EVA based resin and is classifiedinto A1 and A2 types. This type of materials includes EVA resin havingappropriate vinyl acetate content, a melting index and density as a mainmaterial. A foaming agent, a cross-linking agent, pigments, a variety offillers, and functional additives are selectively added into and mixedwith the main material depending on the foam application and fabricationprocess. Table 1 of Type A (unit: Phr) Use Material of Compound Type A1Type A2 EVA resin EVA (VA 21%) 100 — EVA resin EVA (VA 15%) — 100foaming agent AC based foaming agent 12.0 15.5 cross-linking agent DCP(dicumyl peroxide) 1.0 0.5 filler MgCO₃ 6.0 3.5 additive Stearic acid0.8 1.0 pigment Pigment 0.05 0.05

Type B: This type is classified into type B1 and type B2. The type B1adopts an EVA based resin as a main material and includes polyethyleneresin among the variety of synthetic resins as a sub material. On thecontrary, the type B2 adopts the polyethylene resin as a main material,and includes the EVA based resin as a sub material. Furthermore, similarto the type A, a foaming agent, a cross-linking agent, pigments, avariety of fillers, and functional additives are selectively added intoand mixed with the main and sub materials.

The main and sub materials for the type B are not confined to the EVAbased resin and the polyethylene based resin, but many differentsynthetic resins such as polypropylene based resin, polyisobutylenebased resin or poly olefine based resin may be selected as the main orsub materials. Table 2 of Type B (unit: Phr) Use Material of CompoundType B1 Type B2 EVA resin EVA (VA 15%) 95.0 10.0 synthetic resin LDPE(low density 5.0 90.0 polyethylene) foaming agent AC based 1.0 14.0cross-linking agent DCP (dicumyl peroxide) 8.0 0.8 filler CaCO₃ 7.0 —pigment Pigment 0.05 0.05

In case a composite material of the type B2 is cross-linked and foamedby an electron irradiation method, DCP (dicumyl peroxide) that is a kindof organic peroxide based cross-linking agent may be excluded.

Type C: For the main material, this type may include a variety ofsynthetic resins, such as an EVA based resin and polyethylene basedresin, a natural rubber, or a synthetic rubber such as styrene butadienerubber (SBR), poly-butadien rubber (BR), nitrile rubber (NRB),polyisoprene rubber, butyl rubber (IR), chloroprene rubber (CR),neoprene rubber (CR), EPDM rubber, polymer blended NBR, acryl rubber(AR), Urethane rubber (UR), and silicon rubber (SR), etc. A foamingagent, a cross-linking agent, pigments, a variety of fillers, andfunctional additives are selectively added into and mixed with such mainmaterials. This type C is classified into type C1, C2, C3, C4 and C5.Meanwhile, the type C4 and C5 include at least one of a variety ofnatural and synthetic rubbers as a main material, and additionallyinclude a foaming agent, a cross-linking agent, pigments, a variety offillers, and functional additives as a sub material. Table 3 of TypesC1, C2 and C3 (unit: Phr) Use Material of Compound Type C1 Type C2 TypeC3 Synthetic resin EVA (VA 15%), PE(LDPE) EVA 90.0 EVA 90.0 PE 50.0rubber Synthetic rubber EPDM-5.0, SBR-10.0 EPDM-20.0 IR-5.0 Syntheticresin AC based(C1, C2), DPT based(C3) — — 30.0 foaming agent DCP(dicumyl peroxide) 3.5 4.0 4.0 Cross-linking MgCO₃ 0.8 1.0 0.9 agentfiller MgCO₃ 15.0 15.0 40.0 clay — — 40.0 additive paraffin wax — — 10.0zinc oxide 2.0 1.5 — stearic acid 1.0 1.0 1.0 titanium oxide 2.0 3.0 —

Table 4 of Types C4 and C5 (unit: Phr) Material of Compound Type C4 TypeC5 SBR rubber 30.0 — Neoprene rubber 70.0 100 Carbon Black 10. —ZE-O-SIL 10. 10.0 Tellus-oil — 23.0 Stearic Acid 5.0 1.5 Paraffin-oil30.0 — Diethyl thiouria 2.5 — Zinc dimethyl dithiocarbamate 1.7 — SRF —10.0 Clay — 5.0 MgO 20.0 3.0 ZnO 10.0 — Sulfur 1.3 0.2 Blowing Agent 9.010.0

First Embodiment

FIG. 1 illustrates a manufacturing process of a cross-linked foam havingmore than one internally-formed surface according to a first embodimentof the present invention.

Material Preparation: Three sheets of film type materials 111 a, 111 band 111 c having a foaming rate of 150%, which are calender-molded, arecut to have the size of thickness 2 mm, width 100 mm, and length 100 mm.

Interfacing Pattern Formation: A silkscreen printing is performed onboth sides of the first film type material 111 a among the three sheetsof film type materials 111 a, 111 b and 111 c. Interfacing patterns 121a and 121 b are printed on the first film type material 111 a in athickness of 70 micrometers by using a urethane-resin-based ink and theresultant structure is dried at a temperature of 60 degrees Celsius for15 minutes. The interfacing patterns 121 a and 121 b have five-stripedpattern shapes each having a width 2 mm and a length 50 mm, and each ofthe five-striped pattern shapes are spaced apart from each other by adistance of 8 mm.

Foaming Process: FIG. 1 shows a compression-press cross-linked foammolding method. In this method, the film type materials 111 b and 111 care joined to the top and bottom surfaces of the first film typematerial 111 a, respectively, thereby obtain a combination 110. Theweight of the combination is measured, and the combination 110 isinjected into a cavity 131 of a molding die 130 which has a width 100mm, a length 100 mm, and a depth 6 mm. Then the combination 110 isheated and pressed for 480 seconds at a temperature of 150 to 160 degreeC. under a pressure of 150 Kg/cm², such that the film type materials 111a, 111 b and 111 c are cross-linked and foamed.

Thereafter, the pressure is released, and sequentially the molding die130 is quickly opened, thereby foaming the combination 110 to fabricatea foam 140. At this time, the foam 140 is foam-molded in accordance withthe shape of the cavity 131 of the molding die 130. Therefore, theinternally-formed surfaces 142 a and 142 b each forming the inner cavity143 are formed at the intermediate portion of an inside 141 of the foam140 correspondingly to the shape (stripes) of the interfacing pattern121. Since the interfacing pattern 121 are consisting of thefive-striped patterns each of which has a width 2 mm and a length 50 mm,five upper and lower inner cavities 143 are formed in the inside 141 ofthe foam, wherein each of the internally-formed surfaces 142 a and 142 bis a tube type having a diameter 3 mm and a length 75 mm. Due to thedistance of 8 mm among the five-striped patterns, there are formedmembranes, i.e., a cross-sectional portion between neighboring stripedpatterns 141, each of which has a width of 12 mm. The internally-formedsurfaces 142 a and 142 b and the inner cavities 143 are formed in thefoam irrespective of the shape of the cavity 131 of the molding die 130,but has a correlation with the interfacing pattern 121. The foam 140 hasa dimension of width 150 mm, a length 150 mm, and a thickness 12 mm.

Second Embodiment

FIG. 2 illustrates a manufacturing process of a cross-linked foamaccording to a second embodiment of the present invention. The secondembodiment is a modification of the first embodiment in which adouble-layered internally-formed surfaces are formed in the foam.

Material Preparation: Three sheets of white materials 211 a, 211 b, and211 c having a foaming rate of 150% are injection-molded.

Interfacing Pattern Formation: Each surface of the first and secondwhite materials 211 a and 211 b is pad printed to form first and secondinterfacing patterns 221 and 222. The first interfacing pattern 221 isformed on the first white material 211 a, and has nine doughnut typepatterns each of which has an inner circle having a diameter of 2 mmarranged at the center of the doughnut type pattern and an outer circlehaving a diameter of 6 mm. The second interfacing pattern 222 is formedon the second white material 211 b, and is designed with sixteen circlepatterns each having a diameter of 2 mm. The interfacing patterns 221and 222 are printed by a thickness of 20 micrometers using acrylic-resinink, and then thermal-dried at a temperature of 25 degrees Celsius for30 minutes.

Foaming Process: In case of injection molding, the third material 211 cis inserted between the printed surfaces of first and second materials211 a and 211 b, thereby forming a combination 210. Then, thecombination 210 is disposed into a molding die 230, and the molding die230 is closed. A black-particle-type material 212 is injected into aresidual space 234 of the molding die 230. The black-particle-typematerial 212 is heated, softened and melted in a material injector 232at a temperature of 80 to 100 degrees Celsius before it is injected.Thereafter, the combination 210 and the injected material 212 are heatedand pressed for 420 seconds at 170 degrees Celsius under a pressure of6.5 Kg/cm² so as to prepare for a foaming process.

Thereafter, the pressure is released and subsequently the molding die230 is quickly opened, thereby obtaining a single foam 240 having blackand white colors derived from the combination 210 and material 212. Thefoam 240 has first and second internally-formed surfaces 242 and 244forming an inner cavity 243 in an inside 241 of the foam 240. The firstinterfacing pattern 221 constituted by the nine doughnut type patternson the material 211 a becomes nine first internally-formed surfaces 242each having a width of 3 mm and a diameter of 9 mm. Sixteen secondinternally-formed surfaces 244 each having a diameter of 3 mm are formedat the inside 241. The second internally-formed surfaces 244 are derivedfrom the second interfacing pattern 222 having the sixteen circlepatterns.

Third Embodiment

FIG. 3 illustrates a manufacturing process of a foam according to athird embodiment of the present invention. The third embodiment is amodification of the second embodiment.

Material Preparation: Two sheets of materials 311 a and 311 b having afoaming rate of 150% are extrusion-molded or calender-molded. Each ofthe materials has a width of 40 inches, a length of 10 yards, and athickness of 2 mm.

Interfacing Pattern Formation: Peanut-shaped patterns 321 constituted bya pair of adjacent circles each of which has a diameter 6 mm, arearranged on the first material 311 a. Each of the adjacent circles ofthe peanut-shaped patterns 321 has a centric circular opening having adiameter of 2 mm. Each of the peanut-shaped patterns are printed using aepoxy-resin-based ink on the first material 311 a at a thickness of 40micrometers with a margin of 10 mm from the up-and-bottom andleft-and-right neighboring peanut-shaped patterns, and thermal-dried ata temperature of 60 degrees Celsius for 15 minutes.

Foaming Process: In case when the chemical or electron irradiationmethod is adopted, the second material 311 b where the patterns 321 arenot printed is temporarily joined and attached to the first material 311a through a compression roll and the like. Alternatively, a sheet typematerial rather than the second material 311 b is attached to thesurface of the first material 311 a. Thus-obtained combination 310 isprepared in the step prior to a heating process in case of chemicalcross-linked foam molding and in the step prior to an electronirradiation process in case of electron irradiation cross-linked foammolding. The combination 310 is heated and then cross-linked at atemperature 180 to 200 degrees Celsius through the chemical cross-linkedfoam molding, or irradiated by electron beams and heated through theelectron irradiation cross-linked foam molding, thereby permitting thecombination 310 to be foamed as a plane type foam 340. In an inside 341of the plane type foam 340 which is foamed uniformly and continuously ina thickness of 6 mm, a peanut-shaped internally-formed surface 342 thatforms an inner cavity 343 having a length of 9 mm and two columns 345each of which has a width of 3 mm in between the portions of the innercavity 343 are formed. The peanut-shaped internally-formed surfaces 342are spaced apart from each other by a distance of 15 mm in the inside341.

The inner cavity structures in the foams formed by the above-describedfirst to third embodiments have shapes, densities, and structuresindependently from the shape of the molding die.

Fourth Embodiment

This fourth embodiment is to provide a method of controlling pressureand volume of a space, i.e., an inner cavity, formed by aninternally-formed surface having a wide variety of shapes. Additionally,this embodiment forms the interfacing patterns by adding a foaming agentto the interfacing material (ink) so as to efficiently control pressureand volume of the air layer in the inner cavity.

A first foaming agent blended with the foaming material is desirably thesame as a second foaming agent contained in the printed film in a way ofa kind, a grade and a decomposition temperature, and those two foamingagents are simultaneously decomposed at a predetermined temperature.Such foaming agent of this embodiment is an AC based foaming agenthaving azodicarbonamide as a main component, which has a decompositiontemperature of 155±3 degrees Celsius and a gas generation amount of 160to 180 ml/g. The first foaming agent blended with the foaming materialand the second foaming agent contained in the printed film aresimultaneously decomposed at a predetermined temperature such that apredetermined amount of gases, such as nitrogen and carbon dioxide, isgenerated. Thus, the inner cavity filled with such gases is formedinside of the foam at a position corresponding to the interfacingpattern.

The following table 5 shows a comparison of volume and repulsiveelasticity of the inner cavity and a specific gravity of foam inaccordance with the contents of foaming agent in the interfacingmaterials. TABLE 5 Influences of foaming agent contents on a foamFoaming Agent Volume of Inner Repulsive Content(%) Foam Density (g/cc)Cavity (Cm³) Elasticity (%) 0 0.26 1.35 50 10 0.24 2.02 53 20 0.22 2.7056

FIG. 4 illustrates a manufacturing process of a cross-linked foamaccording to the fourth embodiment of the present invention.

Material Preparation: Four sheets of materials 411 a, 411 b, 411 c and411 d having a foaming rate of 150% are formed and cut into sizes eachhaving a thickness of 2.5 mm, a width of 100 mm, and a length of 100 mm.

Interfacing Pattern Formation: Stripes, each of which has a width 3 mmand a length 80 mm, are arranged in vertical and horizontal directionsand spaced apart from each other by a distance of 20 mm on a surface ofthe first material 411 a. A designed pattern 412 including such stripesalso has circles having a diameter 5 mm at crossing points of thestripes. An air passage 413 having a width of 2 mm and a length of 5 mmis attached to a bottom line portion of the designed pattern 412.Usually, the designed pattern 412 is screen-printed using a rubber-basedink so as to form an interfacing pattern having a thickness 70 m, andthen dried.

Foaming Process: The second material 411 b is disposed on the printedsurface of the first material 411 a, and the third and fourth material411 c and 411 d are sequentially disposed on a surface of the firstmaterial 411 a opposite to the printed surface, thereby completing acombination 410. Thereafter, the combination 410 of the first to fourthmaterials 411 a-411 d is disposed into a cavity of a molding die havinga depth of 10 mm, a width of 100 mm and a length of 100 mm, and thenheated and pressed so as to be foamed. Accordingly, the resultant foam410 has a thickness of 15 mm, a width of 150 mm and a length of 150 mm.An internally-formed surface 442 of the foam 410 has an air injectionpassage 445 inside of the foam at a depth of 3 mm measured from asurface 444 of the foam 410. The inner cavity structure 443 formed bythe internally-formed surface 442 serves as air passage. The innercavity structure 443 is formed in the size of a width of 120 mm and alength of 120 mm, respectively. An air injector 450 is connected to theair passage 445, and air of appropriate pressure is injected. A portion446 of the resultant foam 410 where the air injector 450 has passed isclosed by an attachment 460 applied in such a manner as meltingattachment or high-frequency attachment, whereby it is possible toobtain the foam in which the air pressure and the volume of the innercavity structure are controlled properly.

Fifth Embodiment

This fifth embodiment is a modification of the fourth embodiment, andprovides an ability of controlling pressure and volume of a space formedby an internally-formed surface at FIGS. 5 a and 5 b show a cross-linkedfoam according to the fifth embodiment of the present invention

FIG. 5 a shows a structure utilizing a single check valve 532. When apressure 510 repeatedly presses a foam 540, the space (the inner cavity)formed by the internally-formed surface 542 shrinks and thensubsequently an external air 520 is introduced into the space formed bythe internally-formed surface 542 through an air passage 530 and thecheck valve 532, thereby controlling the pressure and volume of thespace formed by the internally-formed surface 542. FIG. 5 b shows astructure utilizing two check valves 532 and 538. An amount of air lessthan that of air introduced through the first check valve 532 isdischarged from the space formed by the internally-formed surface 542 ofthe foam 540 through a second air passage 536 and the second check valve538 during the re-contraction operation of the space formed by theinternally-formed surface 542. Therefore, the structure having the twocheck valves 532 and 538 controls the pressure more efficiently thanthat of FIG. 5 a. In the fifth embodiment, more than one air passagesare formed in the foam, and a variety of check valves are attached tothe air passages, thereby obtaining the foam having the increasedbuffering abilities and the air suction/discharge functions withoutarranging an additional air bag or pump in the foam.

Sixth Embodiment

FIG. 6 illustrates a manufacturing process of a foam according to asixth embodiment of the present invention. The sixth embodiment is amodification of the fourth embodiment.

Material Preparation: Two film-typed materials 611 a and 611 b having afoaming rate of 200% are calender-molded. Each of the first and secondfilm-typed materials 611 a and 611 b has a width of 40 inches, a lengthof 10 yards, and a thickness of 2 mm.

Interfacing Pattern Formation: A designed pattern that is the same asthe designed pattern 412 of the fourth embodiment is gravure-printed ona surface of the first film-typed material 611 a at a thickness ofapproximately 40 micrometers using an epoxy-resin-based ink. The patternis spaced apart from side edges of the first film-type material 611 a bya distance of 1 inch.

Foaming Process: The second film-typed material 611 b is attached to afront surface of the first film-typed material 611 a where the designedpattern is printed using a pressure roll, thereby forming a combination610 of the first and second film-typed materials 611 a and 611 b. Thecombination 610 obtained by temporarily attaching the material 611 b onthe printed surface of the materials 611 a is foamed by a chemicalmethod or an electron irradiation method. The internally-formed surfaceof the resultant foam is almost the same as those of FIG. 4.Furthermore, the air injection method is also the same as that of thefourth embodiment as described referring to FIG. 4.

Seventh Embodiment

FIG. 7 illustrates a cross-linked foam having an air ventilatingstructure to improve a buffering function and an air permeabilityaccording to a seventh embodiment of the present invention. The foammanufactured by the seventh embodiment has an internally-formed surfaceforming an inner cavity structure that is capable of sucking ordischarging air.

Material Preparation: Two film-type materials 711 a and 711 b having afoaming rate of 150% are calender-molded, and then cut into a sizehaving a thickness of 2 mm, a width of 1001 mm and a length of 100 mm,respectively.

Interfacing Pattern Formation: Circular patterns each having a diameterof 5 mm and a thickness of 50 micrometers is formed on the firstfilm-type material 711 a by way of printing a rubbery ink. The circularpatterns are disposed in the range of 160 mm² (80 mm×80 mm) with amargin of 10 mm from the side edges, and spaced apart from one anotherby a distance of 10 mm. The printed circular patterns become aninterfacing pattern 712.

Foaming Process: A second film-type material 711 b is attached to thefirst film-type material 711 a to cover the printed interfacing pattern712, thereby forming a combination thereof. The thus-obtainedcombination is inserted into a cavity of a molding die which has a depthof 4 mm, a width of 100 mm and a length of 100 mm, and then the moldingdie presses and heats the combination to form a foam 740. Afterreleasing the pressure and heat, the resultant foam 740 has a thicknessof 6 mm, a width of 150 mm and a length of 150 mm. Thereafter, a punchforms three holes 742 each having a diameter of 1 mm from a foam surfaceto an internally-formed surface 744.

The foam 740 produced by this seventh embodiment has not only theinternally-formed surface 744 but also columns 746 with the area rangeof 120 mm width and 120 mm length. Each of the columns 746 has adiameter of 7 mm and is spaced apart from the neighboring columns by adistance of 15 mm. Inner cavities 745 formed by the internally-formedsurfaces 744 are connected to each other.

When a pressure P is applied from an external source to the foam 740, anair 750 in the inner cavity 745 is discharged to the outside through theholes 742. On the contrary, when the pressure P is released, the shapeand volume of the foam 740 are restored by the restoring forces of thecolumns 746 as sucking an outside air 752 into the inner cavity 745.

According to the seventh embodiment, it is possible to manufacture afoam that is capable of sucking or discharging air only by thecontracting/restoring action of the foam, which is controlled byadjusting the volume of the inner cavity and the size and number ofholes provided therein for air suction and discharge. It is alsopossible to form the internally-formed surface in a multi-layeredstructure and a second internally-formed surface between the surface ofthe foam and the internally-formed surface so as to insert a thinsynthetic resin plate into a space formed by the secondinternally-formed surface. The foam manufactured by the seventhembodiment can be applied widely to products which require shockabsorbing forces and air permeability, such as shoe components,protective equipment, bed, chair, bag, floor material and sound proofmaterial.

Eighth Embodiment

FIG. 8 illustrates a manufacturing process of a cross-linked foamaccording to an eighth embodiment of the present invention. In theeighth embodiment, the same or different materials are inserted into aspace formed by an internally-formed surface having a variety of shapes.

First of all, a foam 840 is manufactured by the method of the fourthembodiment shown in FIG. 4 and is the same as the foam 410. Thereafter,an air hole 846 having a diameter of 1 mm is punched to an air injectionpassage 845 that is connected to an internally-formed surface 842 of thefoam 840, and another air hole 847 having a diameter of 1 mm is punchedfor smooth injection of a material such as a polyurethane solution. Thefoam 840 having the air holes 846 and 847 is disposed into an aluminummolding die 830, and then a heat is applied to the foam 840 at atemperature of 30 to 40 degrees Celsius.

A polyurethane solution 820 is injected through the injection hole 831of the molding die 830, the air hole 846 and the air injection passage845, such that the air injection passage 845 becomes a polyurethanesolution injection path 845 during the polyurethane solution injectionprocess. Before injecting the polyurethane solution 820, thepolyurethane solution is blended with a polyether-based polyolcontaining isocyanate prepolymer, determined catalytic and foamingagent, in a ratio of 1:3 at a high speed (impellar rpm; 6,000). At thistime of blending, the polyurethane solution 820 has a weight of 25 gthat is determined by multiplying the volume of the space, i.e., theinner cavity 843, formed by the internally-formed surface 842 and adesired specific gravity. Accordingly, the blended material of thepolyurethane solution 820 and the polyether-based polyol is injectedinto the inner cavities 843 through the air hole 846 and thepolyurethane solution injection path 845. After the blended materialinjection, the foam 840 and the injected blended material are cured forabout 8 minutes in the aluminum molding die 830 without applying heatadditionally, and then the foam 840 is de-molded from the molding die830, thereby forming a composite foam 850 integrally interconnected withthe polyurethane. As shown in the cross section of FIG. 8, a compositeinner formed layer 854 including a foamed polyurethane 853 is formed ina grid type structure in an inside 852 of the foam 850. The grid-shapedinner-formed layer 854 is disposed at a depth of 3 mm from a surface 851of the composite foam 850. Additionally, the foamed polyurethane 853filled in the composite inner-formed layer 854 has a diameter of 4 mm.

According to the eighth embodiment of the present invention, a varietyof materials can be substituted for the polyurethane. For example,polyester or polyether based urethane material having a variety ofdensities and molecular structures can be utilized. Further, a varietyof plastic resins, a natural and/or synthetic rubbery material includingurethane rubber, silicon rubber and latex (SBR, NBR, BR, AcrylateLatices), a plaster material, a clay material, or other minerals can beused instead of the polyurethane. Such materials may be injected intothe inner cavities, inserted, joined or attached thereto, and formedintegrally with the foam. Thus-obtained foam can directly be used asindustrial components, or compression re-molded, if necessary, to reformthe shape of the composite foam.

In cases when an EVA based foam and a polyurethane are integrated witheach other, the weaknesses of the polyurethane material, e.g.,decolorization, hydrolysis, bacteria corrosion, and heavy weight, can beeliminated such that a polyurethane material having a variety ofproperties and characteristics is effectively used. As a result, weakproperties of materials are supplemented. Additionally, foams are moldedeven without using an additional molding die in accordance with thestructure of the inner cavities and characteristics of materialsinjected in the inner cavities. Further, manufacturing procedures andcosts can be reduced as compared with a conventional method where foamsof different materials are individually molded and attached with eachother through an additional process.

The following table 6 shows a comparison of properties of compositecross-linked foam with the polyurethane injected into the inner cavitiesformed by the internally-formed surface of the EVA based foam. A letterA denotes the properties between the polyurethane material and the foam,and a letter B denotes the properties between the polyurethanematerials. TABLE 6 Surface hardness Density (Shore 000, Tensile Tearstrength (g/cc) type C) (Kgf/Cm3) (Kgf/Cm3) Repulsive ASTM ASTM ASTMASTM elasticity D-297 D-2240 D-412 D-624 (%) EVA 0.29 52 26 12 41 based(C type) foam PU(A) 0.38 60 4 2 3 (000 type) PU(B) 0.34 62 31 12 33 (Ctype)* Surface hardness is measured by using Shore 000 type for the PU(A)portion, and Asker type C for the EVA foam and the PU(B) portion.

Ninth Embodiment

FIG. 9 illustrates a manufacturing process of a cross-linked foamaccording to a ninth embodiment of the present invention. This ninthembodiment is a modification of the eighth embodiment. In the ninthembodiment, the same and different materials are injected into innercavities formed by the internally-formed surface of a foam, and theinjected materials are molded at both the inner cavities and the outersurface of the foam.

Material Preparation: A sheet of white material 911 a having a foamingrate of 150% is injection-molded.

Interfacing Pattern Formation: A circle pattern having a diameter of 50mm is printed at the center of the material 911 a. Additionally,vertical and horizontal lines having a length of 50 mm are also printedinside the circle pattern along the diametric lines of the circlepattern. The circle pattern and the vertical and horizontal lines areformed of a urethane-resin-based ink at a thickness of approximately 50micrometers, thereby completing an interfacing pattern 912. Thereafter,thus-obtained interfacing pattern 912 is thermal-dried at a temperatureof 60 degrees Celsius for 15 minutes.

Foaming Process: The material 911 a having the printed patterns isdisposed into a cavity of a press type molding die, and then a residualspace of the cavity is filled with a black particle type material 911 bthat has the same foaming rate as the material 911 a. After disposingthe material 911 a and filling the black particle type material 911 b,the press type molding die is closed, and then the heat and pressure areapplied to the materials 911 a and 911 b therein for foaming, therebyforming a cross-linked foam 940. After curing the foam to stabilize thephysical properties, thus-obtained foam 940 has an internally-formedsurface 944 a and 944 b forming an inner cavity therein that is formedalong the shape of the interfacing pattern 912. The internally-formedsurfaces have the circularly shaped portion 944 a and the linearlyshaped portions 944 b.

The foam 940 having the internally-formed surface 944 a and 944 b ispunched from a surface of the foam 940 to form four holes 942 atpositions where the circularly shaped portion 944 a meets the linearlyshaped portions 944 b. Each of the four holes 942 has a diameter of 2mm. Further, another hole 942 having a diameter of 3 mm is formed at aposition where the linearly shaped portions 944 b cross each other.After the punching process of forming the holes 942, the foam 940 isinserted into a cavity of an injection-type molding die while adjustingthe hole 942 of 3 mm diameter to correspond to a material injection path946 of the injection-type molding die. Thereafter, a nozzle 962 of amaterial injector 960 is disposed to correspond to the materialinjection path 946 of the injection-type molding die, and then amaterial 964 different from the foam material, e.g., a urethane-basedresin, is injected through the nozzle 962. Thus, the material 964 isinserted into the inner cavities formed by the internally-formed surface944 a and 944 b and a residual space of the injection-type molding die.After hardening the injected material 964, the injection-type moldingdie is opened and the foam is de-molded. As shown in FIG. 9, theresultant foam becomes a composite foam that includes the urethane resinin the inner cavities. The urethane resin is extended from the innercavities to a surface of the foam and the urethane resin on the surfaceis shaped along a shape of the cavity of the injection-type molding die.Thus-obtained foam can be directly used as industrial components, orcompression re-molded if necessary, to reform the shape of the compositefoam.

Further, fabric, non-woven fabric, natural/synthetic leather, and/orrubber can be selectively attached to the surface of the cooled andcured foam 940 or a variety of pattern shapes can be attached to thesurface of the foam. Thereafter, the surface of the foam can beperforated and then other materials may be injected into the innercavities formed by the internally-formed surface through perforationssuch that the injected material is extended from the inner cavities tothe surface of the foam.

As described above, materials are injected into the inner cavities 944 aand 944 b and molded integrally at the inside and outer surface of theEVA based foam. This results in aesthetic enhancement and improvement inadhesion strength, product quality, properties and functions.

Tenth Embodiment

FIG. 10 illustrates a manufacturing process of a cross-linked foamaccording to a tenth embodiment of the present invention. In this tenthembodiment, an internally-formed surface of a form is divided into morethan two parts in a wide variety of shapes.

Material Preparation: Four sheets of flat-film-type materials 1011 a,1011 b, 1011 c and 1011 d having a foaming rate of 150% arecalender-molded, and then cut into a shape having a thickness of 2.5 mm,a width of 100 mm and a length of 100 mm. First and secondflat-film-type materials 1101 a and 1101 b each are perforated to formtwo holes 1012 each having a diameter of 2 mm.

Interfacing Pattern Formation: A urethane ink is printed on bothsurfaces of the materials 1011 a and 1011 b in such a manner so thatmargins of 10 mm are arranged from the cutting edges of each direction.The cross section of the perforated portion is also covered by theurethane ink, and selected one side of materials 1011 c and 1011 d isprinted, thereby forming an interfacing pattern 1021. Thereafter,thus-obtained interfacing pattern 1021 is dried.

Foaming Process: The first and second materials 1011 a and 1011 b areattached to each other, and the printed sides of the third and fourthmaterials 1011 c and 1011 d are combined with the combination of thefirst and second materials 1011 a and 1011 b. Thereafter, the resultantstructure is inserted into a cavity of a press or injection type moldingdie 1030, which has a width of 100, a length of 100 mm and a depth of 10mm, and then heated and pressed so as to be foamed, thereby forming afoam 1040 after cooling and curing. The foam 1040 has a width of 150 mm,a length of 150 mm and a thickness of 15 mm. Further, a multi-layeredinternally-formed surface 1042 and two holes 1044 each having a diameterof 3 mm are formed in the foam 1040. Thus, the internally-formed surfaceforming an inner cavity has the multi-layered structure of 120/120/3.5mm. Similar to the ninth embodiment, other materials can be injectedinto and filled in the inner cavities (1042) and the holes 1044.

Eleventh Embodiment

FIG. 11 illustrates a manufacturing process of a cross-linked foamaccording to an eleventh embodiment of the present invention. Thiseleventh embodiment is to provide a method of forming athree-dimensional internally-formed surface having a variety of curvedshapes.

Material Preparation: First and second materials 1111 a and 1111 b areinjection- or compression-molded from a white particle material having afoaming rate of 170%. The first and second materials 1111 a and 1111 bhave bumpy surfaces. Also, a particle type material 1112 having a weightof 20 g is prepared.

Interfacing Pattern Formation: An enamel-based ink is sprayed on bothsides 1113 of the first bumpy material 1111 a except for a maskingportion, and then dried. The sprayed ink has a thickness of 40micrometers.

Foaming Process: The dried material 1111 a is combined with the secondbumpy material 1111 b, and the combination of the first and second bumpymaterials 1111 a and 1111 b is inserted into a cavity 1132 of apress-type molding die 1130. Thereafter, a residual space 1134 of thecavity 1132 is filled with the particle type material 1112. Then, thecombination and the particle type material 1112 are together heated andpressed in the press-type molding die 1130 to be foamed, thereby forminga foam 1140. The foam 1140 has a curved internally-formed surface 1142at an inside 1141, as shown in FIG. 11.

Twelfth Embodiment

FIG. 12 illustrates a manufacturing process of a cross-linked foamaccording to a twelfth embodiment of the present invention.

Material Preparation: A first material 1211 a is injection- orcompression-molded using a particle-type material having a foaming rateof 130%, and second and third materials 1211 b and 1211 c having afoaming rate of 150% are also prepared using the method used to preparethe first material 1211 a.

Interfacing Pattern Formation: A urethane-based ink including a 5%foaming agent is sprayed on a whole surface of the first material 1211 aat a thickness of 30 micrometers, and then dried to provide aninterfacing pattern on the first material 1211 a.

Foaming Process: The first material 1211 a covered by the interfacingpattern is combined with the second and third materials 1211 b and 1211c, and then the combination thereof is inserted into a cavity 1232 of apress-type molding die 1230. Thereafter, the combination is heated andpressed so as to be foamed, thereby forming a foam 1240. Then, theobtained foam 1240 is cooled down and cured, and has internally-formedsurfaces 1241 and 1243.

Although the first material 1211 a is foamed simultaneously with thesecond and third materials 1211 b and 1211 c, there exists a spacebetween the foamed first material and the foamed second and thirdmaterials due to the fact that the foaming rate of the first material1211 a is lower than that of the second and third materials 1211 b and1211 c by approximately 20%. Therefore, a separated inner part 1242derived from the first material 1211 a can easily be taken out of theinternally-formed surface, and a predetermined space 1250 can beobtained. The formed space 1250 is exposed outward such that other foamof different material can be inserted and filled into this space 1250.

Thirteenth Embodiment

FIG. 13 illustrates a manufacturing process of a cross-linked foamaccording to a thirteenth embodiment of the present invention. Thethirteenth embodiment is to provide an internally-formed surfaceconnected or opened to the outside in more than one direction.

Material Preparation: A film-type material 1311 having a foaming rate of150% is calender-molded to have a size of 1 mm thickness, 20 incheswidth and 20 mm length. Thereafter, the film-type material 1311 is takenup on a roll.

Interfacing Pattern Formation: A colorless PVA resin based ink isgravure-printed onto one surface of the film-type material 1311 at athickness of 30 micrometers so as to form an interfacing pattern 1312,and then the resultant structure having the interfacing pattern 1312 isthermal-dried at a temperature of 60 degrees Celsius for 15 minutes.Thereafter, the dried material is taken up on a re-heating roll 1320that is formed of aluminum and includes a heater.

Foaming Process: The material 1311 wound on the re-heating roll 1320 isinserted into cavities 1331 and 1332 of a press-type molding die 1330where a heater is installed. Each of the cavities 1331 and 1332 has ahalf cylindrical shape, such that a half of the wound material 1311 isinserted into the first cavity 1331 of the upper part of the molding die1330 and the other half of the wound material 1311 is inserted into thesecond cavity 1332 of the other molding die part. After inserting thematerial 1311, the press-type molding die 1330 is closed, and then theinserted material 1311 is heated and pressed at a temperature of 150degrees Celsius under a pressure of 150 kg/cm² so as to be foamed. Afterbeing de-molded from the press-type molding die, a roll-type foam 1340is formed and then sequentially cured at a temperature of 40 degreesCelsius for 2 hours to stabilize the size and the physical properties.After that, the foam 1340 is unwound from the re-heating roll 1320 andthen re-wound on a winding beam 1350, thereby forming a foam having auniform cross section and a continuous shape. This thirteenth embodimentallows a formation of a foam having a uniform and continuous crosssection, which is not obtained through a conventional pressurecross-linked foaming method.

Fourteenth Embodiment

FIG. 14 illustrates a process of manufacturing a cross-linked foamaccording to a fourteenth embodiment of the present invention. Thefourteenth embodiment is to provide an internally-formed surface havinga multiple-plane structure.

Material Preparation: Three sheets of film-type materials 1411 a, 1411 band 1411 c having a foaming rate of 150% are calender-molded using thesame material. Each of the film-type materials 141la-1411 c has athickness of 2 mm. The maximum dimension of each of the first, secondand third materials 1411 a, 1411 b and 1411 c is 100×100 mm. It isdesirable that the first material 1411 a have a width of 100 mm and alength of 100 mm, the second material 1411 b have a width of 90 mm and alength of 90 mm and the third material 1411 c have a width of 80 mm anda length of 80 mm, for example.

Interfacing Pattern Formation: A urethane-base ink is screen-printed onone surface of each of the second and third materials 1411 b and 1411 cwith a margin being spaced apart from the side edges by a distance of 5mm except from a certain edge, thereby forming an interfacing pattern1421. Thereafter, the resultant structure is dried.

Foaming Process: The first to third materials 1411 a-1411 c aresequentially attached in such a manner that the interfacing patterns1421 formed on their surfaces are arranged in an upper direction so asnot to face each other as shown in FIG. 14. The second material 1411 bis inserted between the first and third materials 1411 a and 1411 c,thereby forming a combination 1410. After that, the combination 1410 isinserted into a cavity 1432 of a press-type molding die 1430, and thenheated and pressed to be foamed. After the foaming process, a foam 1440is formed and de-molded from the press-type molding die 1430. And then,the foam is cured and cooled down at a temperature of 40 degrees Celsiusfor 20 minutes.

The foam 1440 has a size of 150 mm width, 150 mm length and 3 mmthickness, and has a bottom surface 1441 a, a middle surface 1441 b anda top surface 1441 c. The bottom surface 1441 a that is larger than themiddle surface 1441 b is derived from the first film-type material 1411a, the middle surface 1441 b that is larger than the top surface 1441 cis derived from the second film-type material 1411 b, and the topsurface 1441 c is derived from the third material 1411 c, whereby thesides of the foam 1440 have steps due to the size difference thereof. Asshown in FIG. 14, the foam 1440 has a double-layered internally-formedsurface 1442 b and 1442 c which is opened in different directions asindicated by arrows. This internally-formed surface shown in FIG. 14could not actually be accomplished by the conventional pressurecross-linked foaming method or normal pressure cross-linked foamingmethod, but this fourteenth embodiment makes it possible.

Fifteenth Embodiment

FIG. 15 illustrates a manufacturing process of a cross-linked foamaccording to a fifteenth embodiment of the present invention. Thefifteenth embodiment is to provide a method in which the foam having aninternally-formed surface is formed on a different material at a time.

Material Preparation: A first film-type material 1511 a iscalender-molded at a thickness of 2 mm and cut into a circular shapehaving a diameter of 10 mm.

Interfacing Pattern Formation: A urethane-resin-based ink is printedonto the circular-shaped material 1511 a in a shape of circle having adiameter of 3 mm and a thickness of 50 micrometers, and then dried toprovide an interfacing pattern on the first film-type material 1511 a.

Foaming Process: A second film-type material 1511 b that also has acircular shape is combined with the first film-type material 1511 ahaving the interfacing pattern thereon, and then a combination 1510 ofthe first and second film-type materials 1511 a and 1511 b is insertedinto a cavity 1532 of a press-type molding die 1530. At this time, oneor more combinations 1510 may be inserted into one or more holes (cavity1532) of the die 1530. After that, the combination 1510 is covered by apolyester-based synthetic textile 1520 having a thickness of 1 mm, andthen a top cover 1531 of the molding die 1530 is closed. The combination1510 is heated and pressed, and therefore a portion of the combination1510, especially the first film-type material 1511 a, is molten,infiltrated into a surface 1521 of the textile 1520 and adhered to thesurface of the textile 1520. Generally, the combination 1510 is foamedin a thick-wise direction when the molding die 1530 is opened, therebyforming a foam 1540.

After the de-molding, the foam 1540 is formed on the surface 1521 of thetextile 1520, and has an internally-formed surface 1542, which is filledwith air, at an inside 1541 of the foam 1540. This fifteenth embodimentcan be applied to polyester-based synthetic fiber, textile, non-wovenfabric, artificial leather and natural leather. Further, the innercavity (internally-formed surface) of the foam can be modified into awide variety of shapes according to the fifteenth embodiment of thepresent invention.

Sixteenth Embodiment

FIG. 16 illustrates a manufacturing process of a cross-linked foamaccording to a sixteenth embodiment of the present invention Thesixteenth embodiment is to provide a method where a material for theinner cavity of a foam is extrusion-molded.

Material Preparation: A red pellet type material, which is formed from amaterial having a foaming rate of 170%, is injected into an extruder andthen heated in a cylinder to be molten. The molten material iscompressed by a screw and discharged through a tube-type die. Thedischarged material is solidified by a cooling device to be a redpipe-type material 1611 a that has pipes each having a 5 mm outerdiameter and a 2.5 mm inner diameter.

Interfacing Pattern Formation: An enamel-based transparent ink includinga 10% foaming agent is injected into the inside of the red pipe-typematerial 1611 a and then coated on the inner surface of the redpipe-type material 1611 a so as to form an interfacing pattern 1620.After that, the enamel-based transparent ink is dried.

Foaming Process: The resultant red pipe-type material 1611 a is cut intopieces such as 5 pieces in this example, and then combined with a whitematerial 1611 b that is similar to the injection- or compression-moldedwhite material 1111 b of the eleventh embodiment, thereby producing acombination 1610. After that, the combination 1610 of the red pipe-typematerial 1611 a and the white material 1611 b is inserted into a cavity1632 of a press-type molding die 1630, and then a residual space of thecavity 1632 is filled with a white particle-type material 1650 that hasthe same foaming rate as the red pipe-type material 1611 a. The insertedcombination 1610 and white particle-type material 1650 are then heatedand pressed so as to form a foam 1640.

During the foaming process, the hollow portion of the red pipe-typematerial 1611 a is recessed and then becomes an internally-formedsurface 1642 having cylinders each having a diameter of 4 mm. Theinternally-formed surface 1642 forms an inner cavity. Namely, the whitefoam 1640 includes the five internally-formed surfaces 1642. And theportion between 4 to 8 mm of diameter is formed in a red color.

Accordingly, the cross-linked foaming methods of the present inventionprovide a wide variety of inner cavity structures integrally formed withthe foam. The cross-linked foam produced by the present invention mainlycomprises a form body and an inner cavity structure at an inside of thefoam body. The shape of the inner cavity structure may be determined bythe internally-formed surface that may be classified into a closed typeand an open type.

In the closed type, the internally-formed surface is disposed inside thefoam body and the internally-formed surface is closed. However, theinternally-formed surface of the open type extends to the surface of thefoam to communicate with the outside.

The foam body may have air passage(s) communicating with the innercavities, such that the air or gas can freely keep up the stream fromthe outside into the inner cavities or vise versa. Further, the foambody may have a valve system in the air passage so as to control a flowof the air, gas or vapor, wherein the valve system may have a checkvalve. The number and shape of the air passage(s) and valve(s) are notlimited, and many other modifications and variations are possible forthem.

One or more of the material that is the same as or different from thefoam body may be filled or inserted into the inner cavity structure.Thus, the foam may have various physical properties depending on itsparts.

FIGS. 17 a to 17 v illustrate diverse examples of the cross-linked foamaccording to the present invention. These foams are formed by themethods of the present invention discussed above.

FIGS. 17 a to 17 j show examples of cross-linked foams that are formedby foaming a combination of flat type materials having interfacingpatterns 1711 a to

and other materials. As shown in FIGS. 17 a to 17 j, each of thecross-linked foams has a foam body 1750 a to 1750 j and an inner cavitystructure formed by an internally-formed surface.

The inner cavity structure of the foams shown in FIGS. 17 a to 17 j maybe filled with gas or air in such a manner that the external gas or airis injected thereto using an injector, e.g., as described with referenceto FIG. 4, thereby properly controlling a pressure of the inner cavitystructure. Further, as illustrated with reference to FIGS. 5 a and 5 b,an air passage communicating with the inner cavity structure may beformed in such a cross-linked form, and a check valve may be installedin the air passage.

FIGS. 17 k to 17 m show examples of cross-linked foams that are formedby way of piling up flat type materials having interfacing patterns 1711k to 1711 m, combining the piled flat type materials with othermaterials, and then foaming the combination. As shown in FIGS. 17 k to17 m, each of the cross-linked foams has a foam body 1750 k to 1750 mand a complex structure of inner cavities that is formed by aninternally-formed surface.

FIGS. 17 n to 17 u show examples of cross-linked foams that are formedby way of foaming a combination of a foaming material (indicated withdots) and a three-dimensional material having interfacing patterns. Asshown in FIG. 17 n to 17 u, each of the cross-linked foams has a foambody 1750 n to 1750 u and a three-dimensional structure 1711 n and 1711u in an inner cavity structure formed by the internally-formed surface.Although FIGS. 17 n to 17 u illustrate the foam body and thethree-dimensional inner formed structure that are simultaneously formedby the foaming process, it is possible that the three-dimensionalstructure is formed separately from the cross-linked foam body and theninserted into the inner cavity formed by the internally-formed surface.

FIG. 17 v illustrates materials having different examples ofthree-dimensional shapes for forming the inner-formed structures ofFIGS. 17 n to 17 u.

Meanwhile, various physical properties are compared between thecross-linked foam produced by the following inventive method and thatproduced by the related art method and are discussed below.

Accordingly to an embodiment of the present invention, urethane ink isprinted by a silkscreen method on a film-type material that has afoaming rate of 150% and a size of 24 mm width, 24 mm length and a 1 mmthickness. The urethane ink is formed at a thickness of 50 micrometers,thereby forming an interfacing pattern having a size of 20 mm width and20 mm length. One sheet of material is formed on a front surface of thefilm-type material, and five sheets of materials are formed on a rearsurface of the film-type material, thereby forming a combination, wherethose materials are the same as the film-type material. The combinationis inserted into a cavity of a molding die, which has a 24 mm width, a24 mm length and a 7 mm depth. After that, the combination is heated andpressed at a temperature of 165 degrees Celsius under a pressure of 150Kg/cm² for 480 seconds, thereby forming a cross-linked foam. Table 7shows some physical properties of the cross-linked foam manufactured bythe above-described method of the preset invention as compared withthose of the foam manufactured by a related art method. TABLE 7difference of properties in each part on a single foam having innercavity structure Foam Surface Repul- Inter- Inner Foam- density hardnesssive face cavity ing (g/cc) (C type) elas- area volume rate ASTM ASTMticity Foam (Cm²) (Cm³) (%) D-297 D-2240 (%) Foam of the 4 1.35 150 0.2635 50 present invention Foam of the — — 150 0.29 50 42 conventionalmethod

The repulsive elasticity is the value of the highest height measuredwhen the metal ball of 16.3 g is dropped from the height of 450 mm andbounced. The surface hardness and the repulsive elasticity are measuredat a surface of the foam near the inner cavity.

As indicated in Table 7, the foam of the present invention according toone example has the same foaming rate as the foam of the related artmethod, but the foam of the present invention has a low surface hardnessand a large repulsive elasticity rather than the foam of theconventional method due to the fact that it has a inner formed cavitystructure in the foam.

When the foam manufactured throughout the aforementioned methodsaccording to the present invention is combined with other material(s)such as fiber and artificial leather and when the combination of suchmaterials is compressed and re-molded, the volume of the foam is reducedat a predetermined compression ratio, and a difference of theproperties, such as the surface hardness and the elasticity, between there-molded portion of the foam and the inner cavity structure filled withair becomes further increased. This shows significant differencesbetween the foam manufactured by the related art foam molding method(i.e., primary process) and the foam manufactured by a compressionre-molding method (i.e., secondary process). The following Table 8 showsan example of such differences. TABLE 8 surface hardness and repulsiveelasticity of the foams Other portion Inner cavity portion FoamingSurface Re- Surface ratio & hardness pulsive hardness Compression (typeC) elas- (type C) Repulsive ratio ASTM ticity ASTM elasticity Foam/Foam(%) D-2240 (%) D-2240 (%) Foam 150 50 42 35 50 (after foam molding) Foam135 58 45 37 55 (after compression re-molding)

Meanwhile, the cross-linked foam manufactured by the above-mentionedmethods of the present invention will be applicable to shoe componentsor other goods in many ways. Hereinafter, as an example only, the widerage of such foam usage in shoes will be described in detail; however,the present invention is not limited to such and is applicable any othergoods or products.

FIGS. 18 a to 18 f illustrate exemplary applications of the cross-linkedfoam of the present invention to many parts of a shoe.

i) Upper—This upper component constitutes the upper part of a shoe, andincludes an outer surface and an inner surface that are attached to eachother. The outer surface is generally made of a natural/syntheticleather, fiber, textile, rubber, non-woven fabric, and/or a syntheticresin, and the inner surface is made of a PU, PE, latex, sponges,non-woven fabric, and/or textile. When the foam or re-molded foam of thepresent invention is combined with the above-mentioned upper component,the weight of the upper (i.e., part(i)) is reduced, and also thesupporting force, air permeability, buffering, insulation, shapestability and tightness are improved. Moreover, such physical propertiescan be differentiated depending on each part of the foam.

ii) Inner sole—This inner sole component is disposed under the socklinerof the shoe, and absorbs the moisture generated from a foot of a wearer.In the related art, the leather, cellulose board, no-woven fabric orother textile is used for this inner sole, or a piece of steel plate anda trimmed sponge are attached to the inner sole of the boots or otherspecialized shoes so as to raise the hardness of the heal portion andthe flexibility of the forefoot portion. However, the inner sole formedof the foam of the present invention reduces the component weight andmakes it possible to obtain the improved air permeability or todifferentiate the flexibility and hardness in each part of component.

iii) Midsole—This midsole is a main component of a sole-bladder for thesport shoes, slippers, sandals or casual shoes, and made of the EVA, PUor rubbers so as to improve the shock absorbance and repulsiveelasticity.

When the foam of the present invention is adopted for the shoe midsole,the weight of the shoe is reduced because the inner cavities formed bythe internally-formed surface contain the air layers. Further, themidsole can be formed of primary foam or a re-molded foam after thecutting, grinding and attaching process, whereby the shoes can have adiverse appearance and various properties and functions.

In one example, the midsole can be easily manufactured by using the foamdescribed with reference to FIG. 8 (the eighth embodiment) where thematerial is injected into the inner cavity so as to produce a complexmidsole combined with a composite material. In another example, themidsole can be easily formed with the foam described with reference toFIG. 9 (the ninth embodiment) where the material injected from anexterior is cross-link-foamed integrally with the inner formed surfaceand the outer surface of the foam.

If the foam of the present invention is properly modified or combinedfor the midsole to achieve the desired properties and design, themidsole can act as and substitute for a later-described outsole.

iv) Outsole—This outsole component is mainly used for shoes that requireresistances against abrasion and friction. The outsole can be easilymanufactured by using the primary-molded foam or the re-molded foam ofthe present invention. As an example, when the foam formed through theninth embodiment is applied to the outsole, the shoes can obtain thelightweight and the various properties and functions.

v) Sock or Sockliner—This component is generally inserted into the shoeand disposed on the inner sole. The sock or sockliner directly contactsthe foot such that this component requires properties such as the shockabsorbing forces, supporting forces, repulsive elasticity, stability andmoisture absorbing forces.

When the foam of the present invention is used for the sock orsockliner, the weight of the shoe is reduced because of the inner cavitystructure and the air layers. For instance, the foam of the presentinvention used for the sock or sockliner allows easy enhancement ofproperties and functions in every part of the sockliner to be acquired.The foam of the present invention is attached to other materials, suchas textile, non-woven fabric and natural/synthetic leather, so as to beused as the sockliner.

vi) Foam padding—This component is a cushioning member for improving thebuffering, wear comfort and heat insulation of the shoes. The foampadding adopting the foam of the present invention can protect theankle, instep and outside of the foot. For instance, the foam paddingcan be easily provided with the improved properties and functions byusing the foam of the present invention.

vii) Stiffener—This component is inserted to the upper so as to preventdistortions of the upper and protect the heel and ankle. The stiffenercan be easily provided with the improved properties and functions byusing the foam of the present invention.

viii) Instep pad or tongue—This component has the similar functions asthe foam padding described above.

ix) Molded component—This component increases the shock absorbingforces, duration forces and supporting forces of the upper so as toachieve the functional enhancement of shoes, or improves the appearanceof the shoe. This molded component is separately molded to be attachedto a portion of the upper. Namely, the molded component can be formed ofthe foam manufactured by the present invention, and coupled to portionsof the upper.

In the related art, a natural/synthetic leather, fiber, textile, rubber,non-woven fabric, or synthetic resin is compression-molded or extrudedin a various shape to be used for such molded component, and then themolded or extruded material is combined with other adhesive buffingmaterial to be attached to the upper. However, the present inventionadopts the foam described above singly or with other re-molded foam, andthen attaches the foam to the upper of the shoe.

FIG. 18 b illustrates an upper formed from an upper material 1810. Theupper material 1810 is first cut into a desired shape, and then the cutmaterial is sewed with and attached to other materials to form the upper1800.

FIG. 18 c illustrates a manufacturing process of a three-dimensionalupper. A film-type material 1820 having a thickness of 1 mm covers ametal last 1830 that has a foot shape. Then, the metal last 1830 coveredby the film-type material 1820 is inserted in a cavity 1840 of a moldingdie, and foamed by the pressure cross-linked foaming method of thepresent invention. Therefore, the three-dimensional upper is completed.

FIG. 18 d illustrates an upper obtained by attaching or sewing the innersole to the three-dimensional upper of FIG. 18 c.

FIGS. 18 e and 18 f are cross sectional views illustrating a shoe thatis obtained by attaching a midsole, an outsole and a sockliner to thethree-dimensional upper of FIG. 18 d.

The above-described components are used herein so as to effectivelyexplain embodiments of the present invention, and the types of shoes arenot restricted by those components. The components can be selectivelyused or modified so as to manufacture shoes of a wide variety of usesand designs. For example, the upper can be simply connected to themidsole so as to manufacture slippers and sandals. The components can beapplied to in-line skate shoes or ski shoes.

Examples of Upper Structure

FIGS. 19 a to 19 e illustrate exemplary applications of the cross-linkedfoam of the present invention to an upper of a shoe.

FIG. 19 a shows side and cross-sectional views of an upper that ismanufactured by one of the aforementioned third, thirteenth andfifteenth embodiments. A foam having an inner cavity structure 1911 isindependently disposed on a textile 1912, thereby forming anintermediate structure. An additional stuff 1913, such as textile ornatural/synthetic leather, is attached to the surface of theintermediate structure, and then the intermediate structure includingthe additional stuff 1913 is re-molded or punched to form holes 1914 foran air flow, completing the upper. Other components may be attached tothe upper for decoration.

FIG. 19 b shows side and cross-sectional views of an upper that ismanufactured by one of the aforementioned eighth and ninth embodiments.A material 1922 that is the same as or different from a foam is injectedinto an inner cavity formed by an internally-formed surface 1921.Alternatively, the foam is punched to have a hole 1924 to the innercavity 1921, and the material 1922 is injected into the inner cavity1921 and formed both in the inner cavity 1921 and on the surface 1923 ofthe foam. Therefore, the upper having various properties is completed.Also the upper may be attached with other components.

FIG. 19 c shows side and cross-sectional views of an upper that ismanufactured by one of the aforementioned first and second embodiments.A foam having an inner cavity 1931 is provided, and then a material 1932different from the foam is attached to the foam before or afterperforating to the inner cavity 1931 to form a hole 1934. Also, the foamhaving the material 1932 and the hole 1934 may be re-molded. Thus, theupper having the air circulation system and buffering functional systemcan be obtained.

FIG. 19 d shows an upper that is manufactured by one of the twelfth andfourteenth embodiments. The upper of FIG. 19 d is formed to have an aircirculation system, and combined with other components to improveproperties and functionality.

FIG. 19 e shows an upper that is manufactured by one of the first andsecond embodiments. A foam having an inner cavity 1951 is provided and aperforation process is performed to form a hole 1952 to the inner cavity1951. Thereafter, other desired material 1954 is attached to the foam soas to achieve the improved buffering and heat insulating performances.Thus, the upper of FIG. 19 e is completed.

Examples of Inner Sole Structure

FIG. 20 illustrates an exemplary application of the cross-linked foam ofthe present invention to an inner sole of a shoe. Particularly, threeexamples (a)-(c) of the inner sole are shown. Parts (i)-(iii) of FIG. 20correspond to the examples (a) and (b) of FIG. 20, and part (iv)corresponds to the example (c) of FIG. 20.

The foam having an inner cavity structure 2020 is joined with a material2010, for example, a leather plate, a cellulose plate, a non-wovenfabric, or textile. Thereafter, the foam joined with the material 2010is perforated to form holes 2030 that expose the inner cavity structure2020 (ii) or penetrate the foam (i), such that the foam can have theimproved air ventilation and the moisture discharge. Especially, theexample (b) of FIG. 20 has different flexibility and hardness in theforefoot and heel portions of the inner sole ((ii)-(iii) of FIG. 20).Additionally, the example (c) of FIG. 20 has a required hardness in aspecific desired portion by way of injecting other material(s) 2040 asshown in (iv) of FIG. 20.

Examples of Midsole Structure

FIGS. 21, 22 a and 22 b illustrate exemplary applications of thecross-linked foam of the present invention to a midsole of a shoe. Foamsor re-molded foams, which have a variety of inner cavity structures2110, are shown in (a)-(b) and (i)-(x) of FIG. 21. Holes 2120 are formedin the foams or remolded foams, and a valve 2130 is attached to the foamaround the hole 2120. The examples (v), (vii) and (ix) show that amaterial 2140 different from the foam is injected into the inner cavity2110. The example (x) of FIG. 21 shows a method that separates a portion2150 from the foam or re-molded foam.

FIG. 22 a illustrates different examples of shoes including the midsoleof the present invention, and FIG. 22 b are cross-sectional viewsillustrating various examples of the foam structure of the midsole ofFIG. 22 a. The midsoles of FIGS. 22 a and 22 b are obtained by cuttingor grinding the panel-shaped foam. The obtained midsole can be used inan entire portion 2210 or a part 2220 of the shoe outsole, e.g., in theslippers or sandals. The midsole has an inner cavity structure 2230 thathas a wide variety of shapes, and an inner cavity structure 2240 that isformed of composite materials. The inner cavity structure 2240 can beexposed outward so as to achieve the improved functionality andaesthetic enhancement of the midsole. The present invention permits shoecomponent to be formed by assembling the foam having the cut surface andan inner cavity containing air layers, as shown in an example (ii) ofFIG. 22 a.

Examples of Outsole Structure

FIG. 23 shows exemplary outsoles that adopt the foams of the presentinvention. As shown in different examples (i)-(xi) of FIG. 23, primaryfoam or secondary foam that has a variety of inner cavity structures2310 is used for the shoe outsole. A hole 2320 is formed in such foamsand a valve 2330 is installed in the foam around the hole 2320. Amaterial 2340 different from the foam is injected into the foam to beattached to the inner cavity 2310, or a material 2350 also differentfrom the foam is inserted into the inner cavity 2310.

Examples of Sock or Sockliner Structure

FIG. 24 illustrates exemplary shock or sockliner that adopts the foamsof the present invention. As shown, examples (a), (b) and (c) of FIG. 24show the entire shock, the half of the shock, and the heel part,respectively.

An example (d) of FIG. 24 is a cross-sectional view of a shock where oneor more of a variety of materials 2410 as shown in (i)-(viii) of FIG. 24is attached. A valve 2420 is installed in the foam body of the shock soas to form an inner cavity to inhale an external air. In the forefootpart of the sockliner, a plurality of ventilation holes 2430 are formedin order to achieve the air circulation of the inner cavity structure2440. Namely, the sockliner has the structure where air inlet/dischargecan be repeatedly performed when the volume of the inner cavity 2440contracts/expands by a pressure applied from an external source.

The present invention allows for manufacture of a sock or sockliner thathas a wide variety of air flow directions and structures in accordancewith the structure of the inner cavity.

The examples (i) to (viii) of FIG. 24 are cross-sectional viewsillustrating the sock or sockliner that have a wide variety ofproperties and functions. One or more of the materials 2410 are attachedto a foam body, and a plurality of holes 2430 are formed therein. Amaterial 2450 different from the foam is injected into the inner cavityto achieve the variety of properties and functions.

Examples of Foam Padding or Instep Pad Structure

FIGS. 25 and 26 illustrate different examples ((a)-(d) and (i)-(viii) inFIG. 25, and (a)-(c) and (i)-(vi) in FIG. 26) of exemplary foam paddingand instep pad, respectively, which adopt the foams of the presentinvention. As shown, the foam for the foam padding and instep pad hasair layers 2510 and 2610 in various shapes. Also the foams have foreignmaterials 2520 and 2620 in the inner cavity structure, holes 2530 and2630 penetrating the foam or the inner cavity, and valves 2540 aroundthe holes 2530.

Example of Stiffener Structure

FIG. 27 illustrates an exemplary stiffener that adopts the foam of thepresent invention. Examples (a), (b) and (c) in FIG. 27 are aperspective view, a front view and a cross-sectional view taken alongline A-A, respectively. Examples (i) to (vii) of FIG. 27 arecross-sectional views illustrating various examples of an inner cavitystructure of the stiffer.

In the related art, a lightweight synthetic resin is inserted in theleather and then a cushiony is attached to the leather to form thestiffener. However, the present invention provides a foam 2710 having aninner cavity structure 2720 where a separately-made foam 2730 isinserted (ii) or a foreign material 2740 different from the foam isinjected (iii or iv). The injected foreign material 2740 may extend tothe surface of the foam to form a protrusion 2750. Further, an air layer2760, a ventilation hole 2770 and valves 2780 may be formed installed inthe foam of the present invention so as to control the density andhardness of the stiffener.

Examples of Molded Component Structure

FIGS. 28 a and 28 b illustrate examples of molded components of shoesthat adopt the foams of the present invention. Examples (i) to (iv) ofFIG. 28 a and examples (i) to (iii) of FIG. 28 b are cross-sectionalviews showing different examples of the foams of the molded components.

The molded component of the related art includes a leathery material ora synthetic resin composite, which is designed and cut into variousletters and logos, and a buffering material. However, the moldedcomponent of the present invention adopts a foam that has air layers2810 and/or inserted composite materials 2820 to obtain a variety ofdensities and hardness. Also a foreign material 2830 different from thefoam may be attached or printed onto the molded component. A pluralityof holes 2840 may be formed to the inner cavity structure of the foamaccording to the present invention.

Examples of Employing the Foam of the Present Invention in VariousIndustrial Fields

FIGS. 29 a to 29 t illustrate a wide variety of applications where thefoam of the present invention is employed. It should be noted, however,that the present invention is not limited to such and is applicable toother fields or products. In FIGS. 29 a to 29 t, reference numeral 2910denotes an air layer or an inner cavity structure, reference number 2920denotes an injected material, reference number 2930 denotes foreignmaterials joined with the foam, reference number 2940 denotes a materialmolded independently and inserted into the inner cavity, and referencemark * denotes the portions where the foam of the present invention isapplied.

Particularly, FIG. 29 a illustrates a foam of the present inventionemployed in a laptop computer bag. Additionally, the foam may be appliedto the carrier for the electronics goods, such as camera bags, or thebriefcase, especially in tops, bottoms, and handles of the bags.

FIG. 29 b illustrates a foam of the present invention employed inknapsacks or backpacks. The foam of the present invention may be appliedto a shoulder strap and a back part of a bag. Additionally, the foam maybe used as an internal/external buffering material in golf bags andother sports bags.

FIG. 29 c illustrates a foam of the present invention employed invarious parts of body protective equipment. Here in FIG. 29 c, example(i) shows a helmet, example (ii) shows a glove, example (iii) shows ashin guard or leg protector, example (iv) shows a lower body protector,and example (v) shows a chest protector. Part (vi) of FIG. 29 c arecross-sectional views illustrating modifications of foams usable in FIG.29 c. Additionally, the foam of the present invention may be applied tohelmets, headgears, and ski goggles as an internal/external buffering orinsulating material.

FIG. 29 d illustrates a foam of the present invention employed infishing goods, such as overalls and vests. The foam of the presentinvention can also be applied to a variety of floating equipmentrequiring buoyancy, for example, waterproof and heat insulating articlesand life vests or preservers. The present invention can be applied tovarious aquatic sports equipment fabrication and other leisureindustrial equipment fabrication. Further, the foam of the presentinvention may be used for various fishing components, marine productindustries (e.g., buoys), and other oceanic industrial equipments.

FIG. 29 e illustrates a foam of the present invention employed in a hat.The foam of the present invention can be applied to inner and outermembers for hats and caps.

FIG. 29 f illustrates a foam of the present invention employed in abuilding construction. The foam of the present invention can be appliedto ceiling, wall, and floor appliances, as a soundproof or heatinsulating materials. The foam can also be used in combination withother materials for finishing the indoor of the building.

FIG. 29 g illustrates a foam of the present invention applied to foamtapes. An adhesive 2961 is formed on the foam of the present invention,and then a releasing sheet 2963 is attached to the adhesive 2961,thereby forming the foam tape, as shown in example (i) of FIG. 29 g.Example (ii) shows the cutting process of the foam to form the tapes invarious shapes. Examples (iii)-(vi) of FIG. 29 g are cross-sectionalviews illustrating different the modifications of the foam tapeaccording to the present invention.

FIG. 29 h illustrates a foam of the present invention employed in a headcover of golf club. The foams formed by the aforementioned second,third, eighth or ninth embodiment can be applied to the articlesrequiring shock absorbance, shape recoverability, and internal/externalhardness. The foam of the present invention can be also applied tocovers and cases of musical instruments, tennis rackets, hockey sticks,and baseball bats.

FIGS. 29 i and 29 j illustrate a foam of the present invention used as abuffering member for glasses case and cellular phone case. The foam canbe applied to protective cases for glasses, jewelry, watch, telephone,etc. that are fragile and vulnerable to the shock.

FIGS. 29 k to 29 o illustrate a foam of the present invention employedin various packing articles. The foam of the present invention is usedas heat insulation and reservation material and a shock-absorbingmaterial, such as in suitcases, boxes, containers, compatible boxassembly, and a variety of envelopes.

FIGS. 29 p to 29 s illustrate a foam of the present invention used as acushion member for beds, pillows, chairs, mattresses, mats, etc.Examples (i)-(iv) of a foam usable in various cushioning products areshown in each of FIGS. 29 p and 29 q. Example (iii) of FIG. 29 qespecially adopts a fan 2960 in the foam body, such that the airgenerated by the fan 2960 flows through the inner cavities and then isdischarged to the outside through the ventilation holes, i.e., an airpassage. Thus, the foam of the present invention can be utilized in thearticles requiring the air ventilation system, such as mattresses andcushions. Further, the foam of the present invention can be usedemployed in the bicycle/motorcycle chair, car/train/airplane seats(e.g., FIG. 29 r), and chair back so as to obtain a soft cushion, or inany cushioning product (e.g., (i)-(vi) of FIG. 29 s).

FIG. 29 t illustrates a foam of the present invention employed in partof car equipment. The foam of the present invention can be applied to adoor cover 2971, sun visor 2972, headliner 2973, shelf 2974, trunk 2975,headrest 2976, seats 2977, and vehicle carpet 2978. Additionally, thefoam of the present invention can be used as a sound proof and heatinsulating member or a buffering member for vehicles, ship, and train.Further, it is possible for the foam to be combined with other materialsfor finishing and improving the internal/external appearance of theequipments. Different examples of the foam are shown in (i)-(iv) of FIG.29 t.

Meanwhile, the foam of the present invention may be used for thechildren's toys and sports requisites singly or with combining withother materials. Further, the foam can be employed in a water tank or aflowerpot for controlling the amount of water, in a cover for toiletseat lids, in a supporting member for conveying heavyweight stuffs, andin a tie-on strap for electric wires. Namely, the foam of the presentinvention is effectively applicable to various fields including, but notlimited to, a household supply field, a decorating supply field, asecuring or protecting supply field, and an industrial supply field.

The foam is not limited only in the embodiments of the presentinvention, but the various modifications are possible. The presentinvention can make the foam in various designs, sizes and structures tohave desired properties. Namely, the present invention is not limited tothe above-described embodiments and examples described herein.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-27. (canceled)
 28. A cross-linked foaming method comprising: preparingat least one foaming material for a cross-linked foaming, the foamingmaterial processed to have a plane or three-dimensional shape; formingat least one interfacing pattern on a surface of at least one of thefoaming material using at least one interfacing material that preventschemical and physical interaction between the foaming materials; andforming a cross-linked foam by foaming the foaming material having theinterfacing pattern thereon, the cross-linked foam having a foam bodyand an internally-formed surface.
 29. The method according to claim 28,further comprising combining another foaming material with the foamingmaterial having the interfacing pattern thereon before the step offorming the cross-linked foam.
 30. The method according to claim 28,wherein the foaming material is selected from an EVA-based film andmaterial having a plane or three-dimensional shape with a surfaceroughness to easily form the interfacing pattern thereon.
 31. The methodaccording to claim 29, wherein the foaming material is selected from anEVA-based film and material having a plane or three-dimensional shapewith a surface roughness to easily form the interfacing pattern thereon.32. The method according to claim 28, wherein the foaming material isselected from a group consisting of synthetic resins including anethylene-vinyl acetate (EVA)-based resin and a polyethylene-based resin,a copolymer of resins, a natural or synthetic rubber, and a compositematerial including at least one material selected from the syntheticresins and the copolymer and at least one material selected from thenatural rubber and the synthetic rubber.
 33. The method according toclaim 29, wherein the foaming material is selected from a groupconsisting of synthetic resins including an ethylene-vinyl acetate(EVA)-based resin and a polyethylene-based resin, a copolymer of resins,a natural or synthetic rubber, and a composite material including atleast one material selected from the synthetic resins and the copolymerand at least one material selected from the natural rubber and thesynthetic rubber.
 34. The method according to claim 28, wherein theinterfacing material is selected from a group consisting of liquid phasematerials, solid phase materials, and film-type materials.
 35. Themethod according to claim 28, wherein the interfacing pattern is formedby one of process methods including a printing, a transcription, acoating, a deposition, a spraying, a cloth attachment, an inserting, anattachment and modifications of these process methods.
 36. The methodaccording to claim 28,wherein the interfacing material includes at leastone foaming agent selected from foaming agents that are the same ordifferent kinds of the foaming agent for the foaming material.
 37. Themethod according to claim 28, wherein if two or more interfacingpatterns are formed, each of the interfacing patterns is formed using asame or different material.
 38. The method according to claim 28,wherein the step of forming the cross-linked foam is performed either byusing a pressure cross-linked foaming method, a normal pressurecross-linked foaming method, or a modification thereof.
 39. The methodaccording to claim 38, further comprising adding a material that is thesame as or different from the foaming material to a remaining space of amolding die before the step of forming the cross-linked foam when thestep of forming the cross-linked foam is performed by using the pressurecross-linked foaming method.
 40. The method according to claim 28,further comprising injecting air or liquid material into a space formedby the internally-formed surface of the cross-linked foam after the stepof forming the cross-linked foam.
 41. The method according to claim 28,further comprising re-molding the cross-linked foam after the step offorming the cross-linked foam.
 42. The method according to claim 41,wherein the re-molding is performed together with one of materials thatare the same as or different from the cross-linked foam.
 43. The methodaccording to claim 28, further comprising inserting at least one ofmaterials that are the same as or different from the foaming materialinto a space formed by the internally-formed surface after forming thecross-linked foam.
 44. The method according to claim 41, furthercomprising inserting at least one of materials that are the same as ordifferent from the foaming material into a space formed by theinternally-formed surface before re-molding the cross-linked foam. 45.The method according to claim 42, further comprising inserting at leastone of materials that are the same as or different from the foamingmaterial into a space formed by the internally-formed surface beforere-molding the cross-linked foam.
 46. The method according to claim 43,further comprising re-molding the cross-linked foam after inserting thematerial into the space formed by the internally-formed surface.
 47. Themethod according to claim 28, further comprising after the step offorming the cross-linked foam: forming an air passage extending from asurface to a space formed by the internally-formed surface of thecross-linked foam; and inserting one of materials that are the same asor different from the foaming material into the space through the airpassage.
 48. The method according to claim 41, further comprising beforethe step of re-molding the cross-linked foam: forming an air passageextending from a surface to a space formed by the internally-formedsurface of the cross-linked foam; and inserting one of materials thatare the same as or different from the foaming material into the spacethrough the air passage.
 49. The method according to claim 42, furthercomprising before the step of re-molding the cross-linked foam: formingan air passage extending from a surface to a space formed by theinternally-formed surface of the cross-linked foam; and inserting one ofmaterials that are the same as or different from the foaming materialinto the space through the air passage.
 50. The method according toclaim 43, wherein the different material from the foaming material isselected from a group consisting of gas, liquid and solid materials. 51.The method according to claim 44, wherein the different material fromthe foaming material is selected from a group consisting of gas, liquidand solid materials.
 52. The method according to claim 28, furthercomprising rolling up the foaming material having the interfacingpattern thereon before the step of forming the cross-linked foam. 53.The method according to claim 29, further comprising rolling up thefoaming material having the interfacing pattern thereon before the stepof forming the cross-linked foam.
 54. The method according to claim 28,further comprising adding a different material from the foaming materialto the foaming material having the interfacing pattern before the stepof forming the cross-linked foam.
 55. The method according to claim 29,further comprising adding a different material from the foaming materialto the foaming material having the interfacing pattern before the stepof forming the cross-linked foam.
 56. A cross-linked foam fabricated bythe method of claim
 28. 57. A cross-linked foam comprising: a foam body;and at least one inner cavity structure formed inside the foam body,wherein the foam body and the inner cavity structure are formedsimultaneously.
 58. The cross-linked foam according to claim 57, whereinthe inner cavity structure is connected to at least one surface of thefoam body.
 59. The cross-linked foam according to claim 57, wherein thefoam body includes at least one air passage connected to the innercavity structure.
 60. The cross-linked foam according to claim 59,further comprising a valve at the air passage to control an inflow andan outflow of air and/or moisture.
 61. The cross-linked foam accordingto claim 57, wherein the inner cavity structure is filled with one ormore materials that are the same as or different from the foam body. 62.The cross-linked foam according to claim 57, wherein a molded materialthat is the same material as or a different material from the foam bodyis inserted into the inner cavity structure.